Wireless local area networks (WLAN) have shown improvements in throughput, and a significant drop in deployment costs. Offering flexibility and ease of deployment, WLAN are increasingly popular in residential, commercial, and industrial applications. However, wireless communications, being inherently unreliable, need significant improvements before these technologies can become a viable alternate to wired networks, especially for time-sensitive applications.
The main problem for wireless communication networks is interference. Interference can originate in other similar networks operating in a geographic vicinity and in the same or similar frequency bands or channels. Many existing wireless communication networks are allowed to operate in the same unlicensed frequency bands, and therefore interfere with one another. Some examples include Wi-Fi and Bluetooth (BT) devices, cordless telephone, smart telephones, etc., which operate in the 2.4 GHz or 5.8 GHz unlicensed industrial, scientific and medical (ISM) bands.
Interference may also come from non-communication sources such as microwave ovens, fluorescent light bulbs, and objects in the signal paths, which can causing shadowing and multi-path problems. Most of these factors are generally out of control for the operators of the WLAN. Therefore, the WLAN must be able to adapt to such environments by employing technologies that minimize the effect of interference.
The interference that affects the performance of a WLAN can be classified as wideband interference with a bandwidth of 20 MHz or more from other network devices, and narrowband interference signals, typically 1 MHz or less.
Frequency hopping can minimize the effect of interference by spreading the information signal over multiple frequency channels. Systems with orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) systems can provide reliable communications and increased throughput. Though these technologies have reduced the interference levels significantly, interference is still a major source of performance degradation for the WLAN.
The first step to minimize the effect of the interference is to detect the interference and classify its type, e.g., narrow or wideband or both. Appropriate actions such as changing the operating channel, transmitting during inactive periods of a periodic interference signal, etc., can then be devised. Doing that, however, consumes network resources and adversely affects performance. There must be a well-calculated trade-off between the resources that can be committed to deal with the interference and potential improvements gained in the performance.
However, most conventional methods focus only on an individual source of interference.